CN102651200B - Liquid crystal backlight driving circuit - Google Patents
Liquid crystal backlight driving circuit Download PDFInfo
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- CN102651200B CN102651200B CN201110078850.XA CN201110078850A CN102651200B CN 102651200 B CN102651200 B CN 102651200B CN 201110078850 A CN201110078850 A CN 201110078850A CN 102651200 B CN102651200 B CN 102651200B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
- H05B45/3725—Switched mode power supply [SMPS]
- H05B45/38—Switched mode power supply [SMPS] using boost topology
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- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
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Abstract
The invention discloses a liquid crystal backlight driving circuit which relates to the field of liquid crystal displays. The liquid crystal backlight driving circuit comprises a voltage boosting structure. The voltage boosting structure comprises a capacitor C12, a capacitor C13, an inductor L2, a diode D2, a metal-oxide-semiconductor field-effect transistor Mosfet, a capacitor C11, a capacitor C14, a diode D3 and a diode D4, wherein one end of the diode D3 is connected with one end of the capacitor C13, and the other end of the diode D3 is connected with one end of the diode D4; the other end of the diode D4 is connected with one end of the capacitor C14, i.e. an output end of the circuit, and the other end of the capacitor C14 is connected with the ground; and one end of the capacitor C11 is connected between the inductor L2 and the diode D2, and the other end of the capacitor C11 is connected between the diode D3 and the diode D4. According to the liquid crystal backlight driving circuit, the temperature of a liquid crystal backlight driving circuit board and BOM (Bill of Material) of the circuit can be reduced, and the current driving capability of the circuit can be increased.
Description
Technical field
The present invention relates to field of liquid crystal, relate in particular to a kind of LCD backlight source driving circuit.
Background technology
CRT monitor is a kind of display that uses cathode-ray tube (CRT) (Cathode Ray Tube).Current, flat-panel monitor has been substituted the market place of Traditional CRT Display.Wherein especially swift and violent with the development of liquid crystal display.Liquid crystal display has obtained rapidly consumers in general's favor with advantages such as it is light, thin, resolution is high, high colour gamuts.In the last few years, the theories such as low-carbon environment-friendly became the subject under discussion that countries in the world are talked about gradually, and under this overall situation, the demonstration field take liquid crystal display as representative is also constantly attempting various technology, to reach the object that reduces power consumption, low-carbon (LC), environmental protection.
Along with the raising gradually of LED light efficiency, LED has the very long life-span, and itself does not contain the Hg element that environment is had to very havoc effect.Due to these advantages of LED, it is more and more extensive in the application of backlight of LCD field, utilize the LCD TV product in LED-backlit source and concept environmental protection frivolous with it to conquer a lot of users, LED fluorescent tube becomes the product of ruling backlight lighting tube type gradually.But, also just because of the thin characteristic in LED-backlit source, determined that the circuit that it is driven needs special form.
Frivolous being actually above-mentioned utilizes a kind of LED lamp of marginal mode to put that method to set up realizes, and that is to say that the edge that LED etc. is placed in to display realizes.
More thin for backlight is accomplished, need to reduce the width of LED post, and with present fluorescent tube situation, need to use Metal Substrate PCB and design, Metal Substrate PCB is that one side PCB just means and needs one side cabling.In order to take into account the requirement of cabling and width simultaneously, LED lamp needs series design more often than not.According to the series system of many lamps, general voltage range can be 60～150V left and right.As present volume production technology, input voltage is generally 24V.Just there are two problems in this:
1, the conversion efficiency of 24V～150V.
2, the Primary Component in LED-backlit source is as heat dissipation problem and the price factor of Mosfet (metal-oxide half field effect transistor).
Existing large scale liquid crystal backlight source driving circuit is based on BOOST structure (structure of boosting) design, and this BOOST structure as shown in Figure 1.As shown in Figure 1, traditional B oost structure is as above schemed.The voltage that at this time Vout is ordered is just greater than or equal to V1, and its voltage waveform as shown in Figure 2.Withstand voltage on Mosfet is 150V left and right as seen from Figure 2, therefore can select the withstand voltage Mosfet of 200V.The defect of this circuit is: owing to having used the components and parts that withstand voltage is higher (as Mosfet), therefore the temperature of circuit board is higher, and the BOM of whole circuit (Bill OF Material, the cost of raw material) is higher; And the current driving ability of circuit is not high, namely output current is indifferent.
Summary of the invention
(1) technical matters that will solve
The technical problem to be solved in the present invention is: how to reduce the circuit board temperature of LCD backlight source driving circuit, the BOM of reduction circuit, and improve the current driving ability of circuit.
(2) technical scheme
For solving the problems of the technologies described above, the invention provides a kind of LCD backlight source driving circuit, comprise the structure of boosting, described booster mechanism comprises capacitor C 12, capacitor C 13, inductance L 2, diode D2 and metal-oxide half field effect transistor Mosfet, described circuit also comprises capacitor C 11, capacitor C 14, diode D3 and diode D4
Wherein, one end of diode D3 is connected in one end of capacitor C 13, and the other end is connected in one end of diode D4; The other end of diode D4 connects one end of capacitor C 14, the i.e. output terminal of described circuit, the other end ground connection of capacitor C 14;
One end of capacitor C 11 is connected between inductance L 2 and diode D2, and the other end is connected between diode D3 and diode D4.
Wherein, all elements in described circuit are all to make under the withstand voltage technique of 100v.
Wherein, one end of capacitor C 12 is as the input end of described circuit, and this input end is connected with one end of inductance L 2, the other end ground connection of capacitor C 12.
Wherein, the other end of inductance L 2 is connected in one end of diode D2 and one end of Mosfet, the other end ground connection of Mosfet.
Wherein, the other end of diode D2 is connected with one end of described capacitor C 13.
Wherein, diode D2, diode D3 and diode D4 are voltage stabilizing diode.
Wherein, between capacitor C 13 and diode D3, be connected with inductance L 3.
(3) beneficial effect
The present invention, by having increased voltage-multiplier circuit in existing BOOST structure, has realized the second lift of voltage, and therefore the driving force of circuit is improved; Further, in voltage-multiplier circuit, increase an inductance, as afterflow inductance, thereby further improved current driving ability; And due to above design, can in circuit, use the components and parts that withstand voltage is lower (for example Mosfet), thereby can reduce the temperature of circuit board, and reduce the BOM of whole circuit.
Accompanying drawing explanation
Fig. 1 is existing BOOST structural circuit figure;
Fig. 2 is the voltage oscillogram that in Fig. 1, V1 is ordered;
Fig. 3 is the circuit diagram of the embodiment of the present invention one;
Fig. 4 is the circuit diagram of the embodiment of the present invention two;
Fig. 5 is the charging current oscillogram of Fig. 4;
Fig. 6 is the voltage oscillogram that in Fig. 4, VLX is ordered;
Fig. 7 is Fig. 3,4 fundamental diagram.
Embodiment
Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used for illustrating the present invention, but are not used for limiting the scope of the invention.
Embodiment mono-
Embodiments of the invention one provide a kind of LCD backlight source driving circuit, as shown in Figure 3, comprise the structure of boosting, the described structure of boosting comprises capacitor C 12, capacitor C 13, inductance L 2, diode D2 and metal-oxide half field effect transistor Mosfet (single Mosfet of driving, DRV), described circuit also comprises capacitor C 11, capacitor C 14, diode D3 and diode D4
Wherein, one end of diode D3 is connected in one end of capacitor C 13, and the other end is connected in one end of diode D4; The other end of diode D4 connects one end of capacitor C 14, the i.e. output terminal of described circuit, the other end ground connection of capacitor C 14; One end of capacitor C 11 is connected between inductance L 2 and diode D2, and the other end is connected between diode D3 and diode D4.One end of capacitor C 12 is as the input end of described circuit, and this input end is connected with one end of inductance L 2, the other end ground connection of capacitor C 12.The other end of inductance L 2 is connected in one end of diode D2 and one end of Mosfet, the other end ground connection of Mosfet.The other end of diode D2 is connected with one end of described capacitor C 13.Diode D2, diode D3 and diode D4 are voltage stabilizing diode.
In Fig. 3, VLX point voltage is 75V, and all devices in the circuit that therefore can select can be just that the withstand voltage technique of 100V is done below, and therefore the heat of circuit board reduces.
Foregoing circuit is owing to having increased the second lift of voltage-multiplier circuit (comprising C11, D3, D4 and C14) as voltage, and as shown in Figure 3, the first step is boosted as boosting to V2 by booster circuit from Vin, and second step is from V2, to be raised to VOUT by charging circuit.Between D3, D4, voltage equals (VLX-VD2-VD3), VLX is through repeatedly giving C11 charge and discharge, make voltage between C11 and D3, D4 between VLX to 0 repeatedly, and be (VLX-VD4) through D4 voltage, pass through so the energy storage of C14, make VOUT=(VLX-VD2-VD3)+(VLX-VD4)=2*VLX-VD2-VD3-VD4, three diode D2, D3, D4 pressure drops and be about 1 volt, therefore VOUT has obtained (nearly) second lift with respect to VLX.If there is no second lift, VLX=Vin/ (1-D) (D is Mosfet duty cycle of switching), VOUT=2*Vin/ after second lift (1-D)-VD2-VD3-VD4.Visible, under same dutycycle condition, voltage has improved nearly one times.Therefore the driving force of circuit is improved.But because the energy of this voltage-multiplier circuit transmits by capacitor C 11 completely, the driving force of circuit is not also high especially.Therefore the following examples two have been done further improvement on the basis of embodiment mono-.
Embodiment bis-
As shown in Figure 4, the present embodiment has increased an inductance L 3 (between capacitor C 13 and diode D3) in voltage-multiplier circuit, as afterflow inductance, therefore can further promote the current driving ability of circuit entirety.The characteristic of inductance L 3 is to keep the size of current on its both sides constant, and through its afterflow, when Mosfet disconnects, inductance L 3 is charged, and during Mosfet conducting, inductance L 3 is discharged.Therefore the electric current of inductance L 3 has supplemented output current, so can improve the driving force of overall current.
The simulation result of Fig. 5 shows, owing to having increased inductance L 3, can improve the charging ability of whole circuit, and the 600Khz in Fig. 5 represents the switching frequency of Mosfet.The present invention has also carried out another emulation experiment for embodiment bis-, and as shown in Figure 6, it has shown the voltage waveform that VLX is ordered to simulation result, and simulated conditions is:
Condition: VIN=24V, Vout=135V, Iout=0.36A
Inductance: L2=22uH; L3=6.8uH;
Mosfet: withstand voltage 100V, 3A;
Withstand voltage 150V, the 3A of diode: D2;
Electric capacity: C12=10uf, C14 >=10uf, C11=2.2uf.
With reference to figure 7, when switch (Mosfet) is closed, allow electric current to pass through, V2 is to memory capacitance C11 charging, its storage voltage=V2-VD3.Wherein, the forward conduction voltage that VD3 is D3, probably arrives 0.5V left and right at 0.3V.
When switch (Mosfet) is opened, VLX boosts to V2+VD2, now output voltage VO UT=V2+VD2+V2-VD3-VD4, if the forward conduction voltage of three diodes is consistent, and output voltage VO UT=2V2-VD4.Wherein, the forward conduction voltage that VD4 is D4, can find out, VOUT=2VLX-2VD2-VD4 compares the Vout (being less than or equal to V1) in Fig. 1, and output voltage promotes to some extent.VD2 and VD4 are respectively the tube voltage drop on the diode of D2, D4, probably at 0.3V to 0.5V left and right.
Wherein, the Main Function of Mosfet is as switch, is inductive energy storage.It opens or closes VOUT without impact.Switching frequency is set to 20Khz～5Mhz according to peripheral components and efficiency.
In above two embodiment, output voltage is identical, and only owing to having increased inductance L 3, the transfer function that it has played energy, has improved the current driving ability of circuit.
It should be noted that, circuit of the present invention is particularly useful in 42 cun of above large scale liquid crystal displays.
Above embodiment is only for illustrating the present invention; and be not limitation of the present invention; the those of ordinary skill in relevant technologies field; without departing from the spirit and scope of the present invention; can also make a variety of changes and modification; therefore all technical schemes that are equal to also belong to category of the present invention, and scope of patent protection of the present invention should be defined by the claims.
Claims (4)
1. a LCD backlight source driving circuit, comprise the structure of boosting, described booster mechanism comprises capacitor C 12, capacitor C 13, inductance L 2, diode D2 and metal-oxide half field effect transistor Mosfet, it is characterized in that, described circuit also comprises capacitor C 11, capacitor C 14, diode D3 and diode D4;
Wherein, one end of diode D3 is connected in one end of capacitor C 13, and the other end is connected in one end of diode D4; The other end of diode D4 connects one end of capacitor C 14, the i.e. output terminal of described circuit, the other end ground connection of capacitor C 14;
One end of capacitor C 11 is connected between inductance L 2 and diode D2, and the other end is connected between diode D3 and diode D4;
One end of capacitor C 12 is as the input end of described circuit, and this input end is connected with one end of inductance L 2, the other end ground connection of capacitor C 12;
The other end of inductance L 2 is connected in one end of diode D2 and one end of Mosfet, the other end ground connection of Mosfet;
The other end of diode D2 is connected with one end of described capacitor C 13.
2. circuit as claimed in claim 1, is characterized in that, all elements in described circuit are all to make under the withstand voltage technique of 100v.
3. circuit as claimed in claim 1, is characterized in that, diode D2, diode D3 and diode D4 are voltage stabilizing diode.
4. the circuit as described in claim 1～3 any one, is characterized in that, between capacitor C 13 and diode D3, is connected with inductance L 3.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110078850.XA CN102651200B (en) | 2011-03-30 | 2011-03-30 | Liquid crystal backlight driving circuit |
| US13/433,741 US8653744B2 (en) | 2011-03-30 | 2012-03-29 | Driving circuit for LCD backlight source |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110078850.XA CN102651200B (en) | 2011-03-30 | 2011-03-30 | Liquid crystal backlight driving circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102651200A CN102651200A (en) | 2012-08-29 |
| CN102651200B true CN102651200B (en) | 2014-04-16 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201110078850.XA Active CN102651200B (en) | 2011-03-30 | 2011-03-30 | Liquid crystal backlight driving circuit |
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| US (1) | US8653744B2 (en) |
| CN (1) | CN102651200B (en) |
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| US8711530B2 (en) | 2009-06-30 | 2014-04-29 | Teco-Westinghouse Motor Company | Pluggable power cell for an inverter |
| CN104185336B (en) * | 2013-05-23 | 2017-03-29 | 海洋王（东莞）照明科技有限公司 | Booster type switching regulation circuit and light fixture |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101111987A (en) * | 2005-02-25 | 2008-01-23 | 罗姆股份有限公司 | Step-up/step-down regulator circuit and liquid crystal display device using the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2006271182A (en) | 2005-02-25 | 2006-10-05 | Rohm Co Ltd | Voltage regulator circuit and liquid crystal display using the same |
| US8629660B2 (en) * | 2009-03-06 | 2014-01-14 | Maxim Integrated Products, Inc. | Critical conduction resonant transition boost power circuit |
| KR101875220B1 (en) * | 2011-06-08 | 2018-07-06 | 매그나칩 반도체 유한회사 | Led driver circuit |
| US9155156B2 (en) * | 2011-07-06 | 2015-10-06 | Allegro Microsystems, Llc | Electronic circuits and techniques for improving a short duty cycle behavior of a DC-DC converter driving a load |
| KR102019051B1 (en) * | 2011-10-17 | 2019-09-09 | 엘지이노텍 주식회사 | LED driving circuit |
| US8610371B2 (en) * | 2011-12-22 | 2013-12-17 | Allegro Microsystems, Llc | Circuitry to drive parallel loads sequentially |
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- 2011-03-30 CN CN201110078850.XA patent/CN102651200B/en active Active
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- 2012-03-29 US US13/433,741 patent/US8653744B2/en active Active
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101111987A (en) * | 2005-02-25 | 2008-01-23 | 罗姆股份有限公司 | Step-up/step-down regulator circuit and liquid crystal display device using the same |
Also Published As
| Publication number | Publication date |
|---|---|
| CN102651200A (en) | 2012-08-29 |
| US20120249008A1 (en) | 2012-10-04 |
| US8653744B2 (en) | 2014-02-18 |
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